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WASHINGTON — Ten young whooping cranes and the bird-like plane they think is their mother had flown more than halfway to their winter home in Florida when federal regulators stepped in.

Now the birds and the plane are grounded in Alabama while the Federal Aviation Administration investigates whether the journey violates regulations because the pilot was being paid by a conservation group to lead the cranes on their first migration instead of working for free.

FAA regulations say only pilots with commercial pilot licenses can fly for hire. The pilots of Operation Migration's plane are instead licensed to fly sport aircraft because that's the category of aircraft that the group's small, open plane with its rear propeller and bird-like wings falls under. FAA regulations also prohibit sport aircraft — which are sometimes of exotic design — from being flown to benefit a business or charity.

The rules are aimed, in part, at preventing businesses or charities from taking passengers for joyrides in sometimes risky planes.

"That's a valid rule. They shouldn't be hired to do that. But it wasn't written, I believe, to stop a wildlife reintroduction," Joe Duff, an Operation Migration co-founder and one of its pilots, said. The conservation group has agreed voluntarily to stop flying and has applied to FAA for a waiver.

"We're considering that waiver," FAA spokesman Lynn Lunsford said. He said he didn't know when a decision would be made or whether it would be made before spring, when the birds would return to Wisconsin.

"The same regulations that we're applying to these pilots we're applying to everybody who holds that type of (pilot) certificate," Lundsford said. "The regulations are very clear and anyone who is a pilot holding that certificate is expected to know what the duties, privileges and limitations are."

Operation Migration is part of a U.S.-Canadian partnership of government and private organizations trying to re-establish migrating flocks of whooping cranes. The cranes nearly became extinct, dwindling to only 15 birds in 1941. One flyway has already been re-established, but that flock of over 100 birds is vulnerable to extinction should a disaster strike, Duff said.

The grounded birds are part of the organization's 10-year effort to re-establish an Eastern flyway that disappeared in the late 1800s when the last whooping cranes flying that route died off, he said. Since there were no birds still flying the route, conservationists had to teach young cranes how to make the journey.

The birds are bred and hatched at the Patuxent Wildlife Research Center in Maryland. A small group of conservationists in baggy bird suits that conceal their human features are the first thing the birds see when they begin pecking their way out of their shells. The conservationists also give the birds their first nourishment, thus imprinting themselves as "parent." The first thing they hear is a recording of a crane's brood call combined with the purr of the small plane's engine.

The birds are later transferred to a wildlife refuge in Wisconsin, where they are conditioned to follow the baggy-suited humans and purring plane. By fall, they are ready to begin a 1,285 journey from Wisconsin to two wildlife refuges in Florida. The cranes glide behind the plane, surfing on the wake created by its wings. The pilots are dressed in the same baggy white suits and have a fake bird beak attached to one arm, adding to the illusion that the plane is a bird.

It's a slow trip, primarily because of the plane's limitations. No flying on windy or rainy days. This year, one young whooping crane took a wrong turn and wound up spending a few days with some sandhill cranes in wetlands before being herded back to the flock. Rain kept the flock on the ground 16 days in Illinois.

Then, just before Christmas, FAA officials told Operation Migration that they had opened an investigation of possible violations. The birds are now safely penned in Franklin County, Ala., while conservationists await a decision on their waiver request.

If the waiver doesn't come through, "the only option we can think of as a contingency would be to transport them by ground to release sites in Alabama or in Florida," said Peter Fasbender, a U.S. Fish and Wildlife Service field supervisor in Green Bay, Wis., which is part of the partnership to re-establish the cranes.

But Fasbender says he's confident the young cranes will make it back to Wisconsin in the spring. Once they meet up with other cranes making the journey, he said, they usually don't have a problem.

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